Process for sizing paper in the pulp



Patented Aug. 18, 1925.

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No Drawing.

To all whom it may cmicem: I

,Be it known that I, Josnr PELZER a-citizen of the German Republic, residing at Munich, Germany, have invented new and v useful Improvements in a Process for Siz+ ing Paper in the Pulp, for which -I have filed an application ,-in Germany "June 6,

1922, No. 371,380, and of which the following is a specification. 7

My invention relates to paper making, and has particular reference to a method of sizing paper in the pulp. i

The object of my invention is to provide a method of sizing which may be reliably controlled whereby an increase in efliciency and economy of .material is accordingly effected.

-It is well known that for sizing paper in the pulp, a watery alkaline solution of rosin containing -90 to 95% of rosin acids -may be used, which is added to the paper -pulp in the pulp-engine; Then an. acid solution of aluminum sulphate is added,

7 whereby, according to universal opinion, the

rosin is preci itated throughout the paper in an extreme y finely divided state. Since rosin has no affinity for .ink or similar watery"solutions,,the spreading of the ink along the paper fibres is prevented and the paper is thus made suitable for writing puroses.

According to Illig, the inventor of the rosin-sizing process, whose free rosin theory was subsequently supported experimentally by Wurster (Dinglers Polytechnisches Journal'1877), the sizing is effected only by Upon diluting the rosin soap with water before it is introduced into the pulp-engine, more orless turbid liquids are formed according to the alkali content. This turbidity was explained as resulting from free rosin which, in the case of neutral size, was

Application fled June 1, 1m. swarm. 642,600.

I supposed to have been formed byhydrolysis,

and which, in the case of free-rosinsizes, was believed to be due to the free rosin in an emulsive or very finely divided state.

This. theory was frequently borne out by ractical experience but just as frequently inexplicable failures occurred. In short, it

was impossible sufliciently to control the process, and to avoid failure it was customary to add a surplus amount of size.

I I have found however that the free rosin acid is not formed simply by the hydrolysis of the rosin soap solution but that, according to the concentration, difi'erent quantities of acid salts are produced, anda state of equilibrium is reached between the following reactions:

in which Hs represents the anion of the resin acid. The free rosin formed by hydrolysis is precipitated in the form of large the fibres and then wholly or partly de-' composed by the acid action of the alumi- I num sulphate. Such acid salt as may remain undecomposed has exactly the same effect as free rosin, since the acid salthas even less aflinity for water than rosin.

Because of the temporary existence of this acid salt, until now overlooked, the success of the sizing process has heretofore been more or less a matter of accident. In rosin size supposed to contain free rosin, the latter is not containedv as an emulsion in the rosin soap, but on. the contrary, the size consists of a, mixture of neutral and acid salts of rosin acids in varying amounts. By diluting such sizes, there naturally results in the turbid solution a larger percentage of acid salt than in the case of the hlydrolysis of a neutral soap by solution. his percentage can be increased in both kinds of sizes by partly saturating the alkali when dissolving the soap.

Summarizing, it ma be'said that the reliability and success 0 the sizing process is dependent only upon a correct controlling of the process by a proper choice of concen-.

tration during the action of the soap, and

f a a by a regulation ofthe degree 0 liza- .tion, so that a maximum amount of acid salt is existent during the sizing and precipitation in the pulp-engine, the acid salt alone being effective since it alone is finely 6 enough divided.

What I claim as my invention and desire to secure by Letters Patent is The herein-described method of sizing paper in the pulp, which consists in so controlling the concentration and regulating the alkalization during sizing that a maximum of acid salt of the formula 2o 29 2 2o so 2 signature.

DR. J OSEF PELZER. 

